Projection systems project images from a small display, or light valve, found in a projection device, onto a viewing surface. Although the viewing surface may be any flat surface, using a projection screen as the viewing surface may facilitate reflection of the projected image with detail and contrast suitable for viewing over a wide range of angles. A high-quality projection screen will typically reject a substantial portion of the ambient light surrounding the projection system, while still providing sufficient viewing angles of the projected image.
The images projected by projection systems are capable of being very large, which, in turn, corresponds to the use of a large projection screen. However, some users may find a large projection screen distracting while not in use.